Wells are often drilled for the production of petroleum fluids from subterranean reservoirs. In many cases, a drill bit is connected to a drill string and rotated by a surface-based drilling rig. Drilling mud is circulated through the drill string to cool the bit as it cuts through the subterranean rock formations and to carry cuttings out of the wellbore.
As drilling technologies have improved, “measurement while drilling” techniques have been enabled that allow the driller to accurately identify the location of the drill string and bit and the conditions in the wellbore. MWD equipment often includes one or more sensors that detect an environmental condition or position and relay that information back to the driller at the surface. This information can be relayed to the surface using acoustic signals that carry encoded data about the measured condition.
Systems for emitting these acoustic signals make use of wave generators that create rapid changes in the pressure of the drilling mud. The rapid changes in pressure create pulses are carried through the drilling mud to receivers located at or near the surface. Pressure pulse generators include the use of rotary “mud sirens” and linearly-acting valves that interrupt the flow of mud through the pulse generator. The temporary flow disruption can be used to create a pattern of pressure pulses that can be recorded, interpreted and decoded at the surface.
The MWD signal is typically received by one or more transducers located on a standpipe on the surface. The MWD signals contain multiple frequencies and these signals may overlap with other sources of noise in the wellbore. Mud pumps and other drilling equipment may produce noise that frustrates the process of extracting the MWD signal. Additionally, as the MWD travels through the wellbore and standpipe, the MWD signal may reflect off of tubing and equipment (such as the mud pump). Depending on the signal strength, frequency and location of the recording transducers, the reflected signal may partially or entirely cancel the primary MWD signal. There is, therefore, a need for an improved method and system for recording MWD signals that alleviates the deficiencies experienced in the prior art.